When sending PLplot to a file, the user has the option of generating a "family" of output files for most output file drivers. This can be valuable when generating a large amount of output, so as to not strain network or printer facilities by processing extremely large single files. Each family member file can be treated as a completely independent file. In addition, plrender has the ability to process a set of family member files as a single logical file.
To create a family file, one must simply call plsfam with the familying flag fam set to 1, and the desired maximum member size (in bytes) in bmax. plsfam also allows you to set the current family file number. If the current output driver does not support familying, there will be no effect. This call must be made before calling plstar or plstart.
If familying is enabled, the name given for the output file (on the command line, in response to the plstar prompt, as a plstart argument, or as the result of a call to plsfnam) becomes the stem name for the family. Thus, if you request a plmeta output file with name test.plm, the files actually created will be test.plm.1, test.plm.2, and so on. A new file is automatically started once the byte limit for the current file is passed, but not until the next page break. One may insure a new file at every page break by making the byte limit small enough. Alternatively, if the byte limit is large you can still insure a new file is automatically started after a page break if you precede the call to pleop with a call to plfamadv.
The plgfam routine can be used from within the user program to find out more about the graphics file being written. In particular, by periodically checking the number of the member file currently being written to, one can detect when a new member file is started. This information might be used in various ways; for example you could spawn a process to automatically plrender each metafile after it is closed (perhaps during a long simulation run) and send it off to be printed.
plrender has several options for dealing with family files. It can process a single member file (plrender test.plm.1) or the entire family if given only the stem name (plrender test.plm) It can also create family files on output, rendering to any device that supports familying, including another metafile if desired. The size of member files in this case is input through the argument list, and defaults to 1MB if unspecified (this may be changed during the PLplot installation, however). plrender can also create a single output file from a familied input metafile.